It is known that in a certain number of countries, specific standards must be met in terms of the rinsing of the toilet bowl surface by the flushing water; in Scandinavian countries, in particular, the requirement is that the entire surface be rinsed, while in other European countries, only several dozen square centimeters of the bowl, at most, are allowed not to be rinsed.
An embodiment is known in which the bowl is made of two pieces of ceramic material, glued together; one of the pieces is the bowl per se, while the other is a conduit forming the upper edge of the bowl and including orifices toward the bottom for distributing the water. This embodiment is expensive, and the reject rate in manufacture tends to be high, because of the difficulty of gluing the two pieces of ceramic material together.
In another known bowl, the channel is formed in a single piece with the bowl and has the cross section of an inverted U. The opening of the channel toward the bottom comprises a slit of as narrow a width as possible; it is even preferable to have a variable width from one end to the other of the path of the water, to assure suitable distribution. Since the outflow slit must be narrow, manufacturing problems arise, because the thickness of the walls of ceramic material, which are built up by depositing slip, is essentially a function of time and atmospheric conditions, and the width of the slit derives from the difference between a width that separates two walls of the mold and the thickness of the deposits on these two walls. It is apparent that if the slit must be quite narrow, it is very difficult to gain control over the constancy of the width. Once again, the result is a high reject rate in manufacture.
Bowls are likewise known in which the upper edge comprises a channel in the form of an inverted U that opens downward along a rather wide slit, to enable insertion of a distribution device into the part of the channel that is near the water supply. This distributor device is generally made of a flexible plastic material, because it is difficult to put in place. In fact, the zone that comprises the conduit for water for the bowl is a closed zone disposed vertically of the tank, and this closed zone is supplied through an orifice made in its wall.
In a first variant, the tank comprises a separate piece that is assembled to the bowl, which in turn includes its associated supply conduit molded with it. In a second variant, the tank is molded in one piece with the bowl, in which case the supply conduit comprises the zone included between the two walls forming the bottom of the tank; a double bottom at right angles with the tank in this manner is necessary because the lower part of the tank must include a wall to support the flushing mechanism that controls the delivery of water to the bowl. It can be seen that to install the distributor device, it must be introduced either via the source of supply to the conduit or via the slit of the channel where the supply conduit discharges. The upstream portion of the distributor device must be located in the supply conduit, and its two downstream branches must be disposed symmetrically in the channel (that is, symmetrically with respect to the common plane of symmetry of the bowl and tank), so that the distributor device is difficult to install, which increases the cost price of the toilet system. Moreover, the distributor device is necessarily short in length and so it has limited efficiency; it must also be flexible, so that the material comprising it is likely to deteriorate rather rapidly in contact with the flushing water.